I study the evolutionary genetics of animal behaviour. I focus primarily on the rover/sitter foraging polymorphism found in the fruit fly, Drosophila melanogaster and discovered by Marla Sokolowski in the early 1980s. Rovers eat less but move more than sitters during foraging and they are more likely to explore new food patches than sitters. These behavioural differences arise mainly from allelic variation in foraging (for), which encodes a cGMP-dependent protein kinase (PKG). Rovers (forR) have higher RNA transcript levels and PKG activity levels than sitters (fors). This polymorphism has now become a classic model system in behaviour genetics. My research explores: i) the evolutionary link between foraging behaviour and cGMP-dependent protein kinase, ii) identifying additional genes that influence foraging behaviour, and iii) the maintenance of the rover/sitter polymorphism by frequency-dependent selection.